Centralized traffic controlling system for railroads



T. J. JUDGE June 30, 1936.

CENTR A LIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS l I I l I I I i l I fl k" u NS 25 55:

.53m xvi 8 8 53m 22m Em outc 3.55m

y"; JQQQ T. J. JUDGE June 30, 1936.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Jan. 1'7, 1955 3 Sheets-Sheet 2 INVENTO ATTORNEY June 30, 1936. J JUDGE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Jan. 17, 1933 5 Sheets-Sheet 5 ATTORNEY fi v 1% n 20 53% wnuummw Patented June 30, 1936 curren STATES CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application January 1'7, 1933, Serial No. 652,176

8 Claims.

This invention relates to centralized trafiic controlling systems for railroads and it pertains more particularly to the communication part of such systems. This invention is an improvement over the invention disclosed in the application of 7 Preston Ser. No. 596,516 filed March 3, 1932, and I propose to claim only the improvement herein. The present invention contemplates a centralized traffic controlling system in which the switches and signals at a plurality of stations located along a railroad system are connected to the control ofiice by means of a two-wire line circuit. The switches and signals at the stations are under the supervision of an operator at the control oifice, so that the condition of such switches, signals and various other traflic controlling devices at the distant locations will be transmitted to the control ofiice, for providing the operator with the necessary information for governing train movements. In a system of this type, the switches and signals are associated with automatic block signal means and such other local means as are ordinarily provided to guard against unsafe train movements, improper operation of track switches or the like.

The several outlying track switches and their associated signals located adjacent or near each other, together with the apparatus provided to govern these switches and signals are conveniently referred to as comprising a field station.

In the present invention it is proposed to provide a line battery at the control office and at each field station, for energizing and deenergizing the two-wire line circuit connecting the control office with the field stations, with polar impulses for transmitting outbound communications from the control office, as well as inbound communications to the control office.

Either control impulses are transmitted from the control ofiice or'indication impulses are transmitted from a field station during any particular operating cycle. These impulses are made distinctive by reason of their polarity for the purpose of transmitting the desired controls or indications. The system is so organized that irrespective of the simultaneous occurrence of control and indication conditions, only one location is effective to transmit impulses at any one time. In other words, the control ofiice may transmit control impulses over the line-circuit during an operating cycle and during this cycle, all field stations are prevented from obtaining access to the communication circuit for transmitting indi cation impulses. Likewise, when one of the field stations is transmitting indication impulses to the control office, all other field stations are locked out and the circuits are arranged to guard against the control ofiice breaking in on the line during an indication cycle.

Irrespective of whether the control office ur a vention will be explained more in detail in the following description of one embodiment and various other characteristic features, advantages and functions of a system embodying this invention will be in part pointed out and in part apparent as the description progresses.

In describing the invention in detail, reference will be made to the accompanying drawings, which illustrate one method of carrying out the invention by way of example. The drawings illustrate in a diagrammatic manner the apparatus and circuits employed and for convenience in describing the invention in detail, those parts having similar features and functions are designated in the different figures by like reference characters, generally made distinctive either by the use of distinctive exponents representative of their location, or by the use of suitable preceding numerals representative of the order of their operation and in which:-

Fig. 1 illustrates the two-wire line circuit connecting the control ofiice with a plurality of field stations, together with certain contacts and relays which cooperate in the control of the line circuit and which are schematically illustrated.

Fig, 2 illustrates the apparatus and circuits employed at the control ofiice.

Fig. 3 illustrates the apparatus and circuits employed at one of the field stations.

When tracing the circuits, Fig. 3 should be placed to the right of Fig. 2.

V The illustrations in the drawings are schematic and abbreviated vfor the purpose of clearness and simplicity. The arrangement of those parts of the centralized traffic controlling system, which are not illustrated in the drawings and their cooperation and connection with the illustrated portions, will be set forth in the following general description. After the general description, a detailed description will be given of the transmission of controls from the control office for selecting a field station and for operating controlling devices at the selected station. Likewise, a detailed description will be given of the transmission of indications from a field station, for registering such a station in the control oflice and for thereafter selectively operating indicating devices associated with the registered station in the control ofiice.

General description The symbols and are employed to indicate the positive and negative terminals respectively, of suitable batteries or other sources of direct current and the circuits with which these symbols are used always have current flowing in the same direction. The symbols (3+) and (B) indicate connections to the opposite terminals of a suitable battery, or other direct current source, which has an intermediate tap designated (CN) and the circuits with which these symbols are used may have current flowing in one direction or the other, depending upon the particular terminal used in combination with the intermediate tap For convenience in describing the operation of the system, the two line wires connecting the control ofiice with the stations are referred to as the control line and the return line. The control line is the line in which the line relays at the office and at the stations are connected, as well as the line impulsing contacts of the irnpulsing relay located in the control ofiice. The control line and the return line are connected together at the last station as indicated in Figs. 1 and 3.

At the control oifice, a line battery OB is provided and arranged for being selectively connected to the control and return lines. At each field station a line battery is provided, such as that indicated by reference character FB in Fig. 3. Fig. 1 shows ofiice battery OB and three field batteries FB FE and F3 at the first, second and last field stations respectively. It will be understood that additional stations may be interposed in the line connections between the second and last station.

Control ojfice equipment-The control office (see Fig. 2) includes, besides the apparatus above mentioned, a quick acting line relay F of the polar type, which has its contacts positioned to the right when an impulse is connected tothe line in such a way that potential is applied to the control line in the control office and to the left when potential is applied to the control line in the control oifice. Line relay F will actuate its contacts to the left when potential is applied to the control line at a field station and to the right when a field station applies potential to the control line.

A quick acting line repeating relay FP of the neutral type, is included in the control ofiice and it repeats each energization of line relay F, irrespective of the polarity of the impulse which energizes relay F. In other words, relay FF is picked up each time the line circuit is energized and is dropped between successive impulses.

Slow acting line repeating relay SA is of the neutral type, having such slow acting characteristics that it does not drop away between the successive energizations of relay FP. It is energized at the beginning of a cycle and remains energized throughout the cycle until a predetermined time interval elapses at the end of the cycle. Besides being slow releasing, relay SA is somewhat slowin picking up, but its release period is considerably longer than its pick-up period.

An additional slow acting relay SAP, of a type similar to relay SA is provided for repeating the condition of the SA relay, in such a manner that relay SAP is picked up at the beginning of 9.

cycle of operations and is dropped at the end of a cycle.

Neutral selecting relay S located in the control ofiice, normally connects the control line to the return line in the control ofiice, exclusive of the control ofiice battery. When the contacts of relay S are picked up, polar impulses can be applied to the control line from the control oifice battery, in accordance with the positions of the polar contacts of code selecting relay CS. Relay CS is therefore for the purpose of selecting the polarity of the impulses which the control ofiice applies to the line.

Impulse relay P controls a contact which is included in the control line, for the purpose of applying time spaced impulses to the control line circuit when relay S is picked up, such impulses having polarities as determined by relay CS, all of which will be more specifically pointed out later in the description. A checking relay CK of the neutral type is provided to register or store the particular polarity of the initiating impulse ap plied to the line circuit at the beginning of each cycle of operations.

A bank of stepping relays IV, 2V and LV, to-

.gether with a cooperating half step or steering relay VP, serve to mark off the steps of each cycle of operations. A stepping relay is picked up on each .ofi period, that is, each time the line repeating relay FF is deenergized. The VP relay is shifted on each on period, being picked up during the on period following the picking up of each odd stepping relay and dropped during each on period following the picking up of each even stepping relay. In this description, the periods during which the line circuit is energized are referred to as the on periods and the periods during which the line circuit is deenergized are referred to as the off periods.

The impulsing relay P cooperates with the stepping relay bank and the VP relay, in such a manner that time spaced impulses are applied to the line circuit in accordance with the actual response of the system in the control ofiice.

As typical of the equipment located in the control office, a control machine having a control lever for a field station connected to the line circuit is shown. A miniature track switch ts corresponds to a particular track switch in the field and represents the actual track layout at the field location. Switch machine control lever SML is for the purpose of governing the corresponding track switch at the field station with which it is associated. A starting button SB is provided to be actuated subsequent to the proper positioning of the control levers, for initiating the system for the transmission of controls as set up by the levers. The actuation of lever SML to one position or the other results in the normal or reverse control of the corresponding track switch at the field station, with which this lever is associated.

Additional control levers (not shown) may be associated with each field station for controlling signals at the field stations, but in order to simplify the drawings and description, these devices have been omitted. Indicating lamp OS associated with the miniature track switch is controlled by the passage of a train over the corresponding track section of the field station, to

visually indicate to the dispatcher the occupied or unoccupied condition of the track section.

Indication storing relay IR is controlled in accordance with the occupied or unoccupied condition of the detector track section, as repeated by the track relay at the field station for controlling the OS lamp. It will be understood that relay IR is merely typical of additional indication storing relays which may be provided for storing additional indications repeated by other conditions at the field stations, such as the positions of switch machines, conditions of signals, etc.

For the purpose of illustrating station registration, a typical pilot relay IPT is shown. This provides for registering a station on only one step, but it is apparent that additional pilot relays may be provided for additional steps, up to the point wheresufiicient codes for complete station registration are obtained.

A station relay ST provides for the registration in the control ofiice of the station which is transmitting indications. This relay is merely typical of a number of such relays which would be ordinarily provided, one for each individual station. One other relay similar to relay ST would connect to the back contact of relay IPT, for obtaining a selection of two stations on the first step. By providing an additional pilot relay conditioned on the second step, for example, two more station relays could be connected to obtain a registration of four stations.

A storing relay SR and its corresponding code determining relay CD are associated with the starting button. These and similar relays, which are individual to each station connected to the communication system, are so interconnected that only one CD relay may be up during one cycle of operations. Any number of storing relays may be up, however, for storing the fact that controls are to be transmitted to the stations with which they are associated. This interconnection of the SR and CD relays is so arranged that when several storing relays are up 'at the same time, the corresponding CD relays will be picked up one at a time, during successive operating cycles, in an order predetermined by their relative locations in the relay bank, all of which has been completely disclosed in the prior application of N. D. Preston et a1., Ser. No. 455,304, filed May 24, 1930, corresponding to Australian Patent 1501 of 1931.

Field station equipment-The field station illustrated in Fig. 3- includes a quick acting line relay F of the .polar type and a quick acting line repeating relay FP of the neutral type, which repeat the energizations and deenergizations of the control line. Relay FP repeats the impulses in the control line irrespective of their polarities,

while relay F is actuated to the right by a positive impulse coming over the control line from the control office. Relay F is actuated to the left by a negative impulse coming over the corn trol line from the control ofiice. It follows that a positive impulse applied to the control line at the field station corresponds to a negative impulse applied to the control line in the control office, so that when the field station energizes the control line with a positive potential, relay F will be actuated to the left. Slow acting relays SA and SAP are similar to corresponding relays in the control ofiice and are likewise used to define the bounds of each operating cycle.

The field station includes a lock-out relay LO which is picked up at the field station which is sending indications over the communication line. As will be fully described, the circuits of this lockout relay are so organized, that in the event several field stations have new indications to transmit at substantially the same time, the station nearest the control ofiice obtains connection with the line and others arelocked out. During succeeding cycles, other waiting stations et their chance to transmit indications and take their turns in accordance with their location with respect to the control ofiice.

Relay CS corresponds to relay OS of Fig. 2, since it determines the polarity of each impulse from battery F13 when the station is transmitting. Checking relay CK which corresponds to relay CK of Fig. 2, is picked up when the control oiiice is transmitting and remains down when the associated field station is transmitting. Relay 0K registers or stores the particular polarity with which the line circuit is energized during the initiating period at the beginning of each cycle.

A stepping relay bank including relays lV 2V and the associated half step or steering relay VP is provided and these relays operate in synchronism with corresponding relays in the control office, so that they take one step for each energization of the line for marking off the steps, during which code sending relay CS may be distinctively positioned in accordance with the indications to be transmitted.

A pilot relay PT and a station relay ST operate in a manner similar to corresponding relays located in the control oflice. It will be understood that additional pilot relays and additional station relays may be provided and connected in an obvious manner, as the size of the system demands. A track switch T8 is operated by a switch machine SM of any suitable type. The position and locked or unlocked condition of the track switch may be repeated by the usual switch repeating relay (not shown) and this switch repeating relay may control the indication circuit for transmitting to the control oifice the condition of the track switch. The switch machine SM is remotely controlled by the operator in accordance with the position to which he actuates lever SML of Fig. '2 with such control locally repeated at the field station to the switch machine by the switch machine relay SMRL A change in the condition of the detector track section is repeated by relay T The indication code circuit which is connected to normally open back contact I59 of relay T may be considered typical of the manner in which other indication code circuits are connected to other relays, such as the above mentioned relay which repeats the operation of the track switch.

Change relay CH provides for registering a change in the trafiic controlling devices at the station, so that the system will be automatically started through a cycle of operations for the transmission of new indications whenever this relay .CI-I is down. It willv be understood that relay CH will register a change in one or more of a large number of devices and initiates indication cycles as long as there are new indications to be transmitted. Start relay STR cooperates with relay CH for initiating indication cycles as long as there are new indications to be transmitted.

It is believed that the nature of the invention, its advantages and characteristic features may be best understood with further description being set forth in a manner relating to typical operations of the system.

Operation While the system is at rest or in its so-called period of blank, the line circuit including line wires l0 and Il is normally deenergized. The relays and circuits of the system are normally deenergized with a few exceptions. For example, code sending relay CS in the control oflice (Fig. 2) is normally energized during the period of blank, over a circuit extending from (B+) back contact I2 of relay IV, back contact I3 of relay 2V and winding of relay CS, to (CN). The cur rent which flows in this circuit is effective to position the polar contacts of relay CS to the right as shown.

Change relay CH at the field station (Fig. 3) is normally energized through a stick circuit extending from front contact H4 of relay T front contact H5 of relay CH and lower winding of relay CH to It is to be understood that the detector track section, associated with the track switch TS is a normally energized track circuit, so that the track relay T is normally picked up.

Manual starting.With the system at rest, the operator can initiate a cycle for the selection of a particular station and the transmission of desired controls to the selected station. For example, if he desires to operate the track switch TS he properly positions control lever SML and then actuates the starting button SB. It is to be noted that the operator may precondition the control lever SML (and other similar levers when provided) as desired, without the transmission of controls until the starting button SB is actuated. However, such an arrangement is to be considered as merely one embodiment of the present invention, since the system may readily be arranged to be initiated upon the actuation of one or more control levers, without the need of operating a starting button. Such an arrangement is shown, for example in the prior application of N. D. Preston, Ser. No. 573,079 filed November 5, 1931.

The actuation of the starting button SB, while the system is in the period of blank, causes the energization of the storing relay SR and the code determining relay CD. Relay SR closes a circuit for picking up relay S which extends from front contact I6 of relay SR, back contact I] of relay SAP, back contact I8 of relay CK and winding of relay S, to Relay S, in opening its back contact 24, prevents a field station from transmitting, as later described. After a time, the relay SAP picks up which prevents the picking up of relay CK during the cycle by opening back contact 21. With relay CK down, the operating cycle is marked for the transmission of controls.

Relay S closes a stick circuit for itself extending from front contact 20 of relay SA, back contact 22 of relay CK, front contact 2| and winding of relay S, to This stick circuit maintains relay S picked up until the end of the cycle.

The operation of relay S energizes the control line with potential, over a circuit extending from the side of battery OB, contact 23 of relay CS in its right hand position, front contact 24 of relay S, winding of relay F, back contact 25 of relay P, control line I0, winding of relay F back contact I26 of relay L0 through the control line circuit at other stations along the line, connection I21 at the last field station, return line conductor II, contact 28 of relay CS in its right hand position, to the terminal of battery OB.

This initial impulse, which is referred toas by reason of the position assumed by relay CS, effects the actuation of relays F, F and other line relays similar to relay F at the various stations to their right hand positions.

The energization of relay F closes a circuit from contact 29 of relay F in its right hand dotted position and winding of relay FP, to over which circuit relay FP operates. Relay FP at the field station is similarly operated over a circuit extending from contact I28 of relay F in its right hand dotted position and winding of relay FP to While the description will be more particularly directed to the operation of the circuits of the field station illustrated in Fig. 3, it will be understood that similar circuit operations are effected at other stations substantially in synchronism with those described in connection with the station of Fig. 3. Therefore, the circuit operation of the field station illustrated may be considered typical of other stations not illustrated, with the exception of the code jumper arrangements, which are distinctive for different field stations to provide station selection during control cycles and station registration during indication cycles.

The closure of contact 26 of relay F in either its right or left hand dotted line position is ineffective during a control cycle, because the first impulse actuates relay F to the right, which does not complete an energizing circuit for the upper winding of relay CK. When succeeding impulses operate contact 26, the energizing circuit of relay CK is open at back contact 21 of relay SAP, the latter relay being picked up, as will now be described. The circuit through front contact 21 of relay SAP is open at back contact I9 of relay S.

The closure of front contact 30 of relay FP closes an obvious circuit for picking up relay SA. The closure of front contact 3I of relay SA establishes an obvious circuit for picking up relay SAP. Likewise, at the field station, the closure of front contact I28 of relay FP establishes an obvious circuit for picking up relay SA The closure of front contact I30 of relay SA establishes an obvious circuit for picking up relay SAP Relay SAP by reason of its slow picking up characteristics, maintains its back contact I3I closed for a sufiicient time to allow relay CK to be picked up over a circuit extending from (3+) contact I32 of relay F in its right hand dotted position, back contact I3I of relay SAP and lower winding of relay CK to (B). The actuation of relay SA before the picking up of relay SAP closes a stick circuit for relay CK extending from front contact I33 of relay SA front contact I34 of relay CK and upper winding of relay CK to It is to be noted that the picking up of relay 0K and the consequent opening of its back contact I35 disables the pick-up circuit of relay L0 so that this latter relay can not be picked up during a control cycle. Likewise, the opening of back contact I36 of relay CK prevents the actuation of relay CS during a control cycle.

After the predetermined time has elapsed required for the picking up of the contacts of relays SA, SAP, SA and SAP, the system is then in readiness to be sequentially and synchronously stepped through a control cycle of operations. Since the polarity of the initial impulse placed on the line circuit is for picking up relay 0K and leaving relay LO down at the field station and for picking up relay S and leaving relay CK down at the control office, the nature of the cycle of operations is now determined or fixed as a control cycle.

Line impulsing and stepping relay operation.- As soon as the slow acting relay SAP has actuated its contacts to picked up positions, the control and front contact 43 of relay FP, to (CN).

line is opened by the picking up of relay P over a circuit'extending from front contact 32 of relay SAP, back contact 33 of relay VP, upper winding of relay P, back contact 34 of relay IV, back contact 35 of relay 2V and back contact 35 of relay LV, to Relay P, in operating, opens its back contact 25 which de-energizes the control line to provide the first off period.

De-energizing the control line results in the release of relays F and PP. A circuit is now closed for picking up the first stepping relay IV extending from front contact 31 of relay SA, back contact 38 of relay FP, back contact 39 of relay VP, back contact 40 of relay 2V and winding of relay IV, to Relay IV establishes a stick circuit for itself extending from front contact 31 of relay SA, front contact M of relay IV and winding of relay IV, to

Relay IV opens the above described circuit through the upper winding of relay P, which allows this latter relay to release and again energize the control line conductor for the next on period. Relays F and FF again pick up and a circuit is closed for picking up relay VP which extends from (13+), front contact 42 of relay IV, back contact "33 of relay 2V, lower winding of relay VP and front contact 44 of relay FP, to (CN). Relay VP establishes a stick circuit for itself extending from front contact 31 of relay SA, front contact 45 of relay VP and upper winding of relay VP, to It is to be noted that current flowing through the upper winding of relay VP by way of this stick circuit, is in the same direction as just described in connection with its pick-up circuit through its lower winding.

A circuit is now closed for again picking up relay P extending from back contact 36 of relay LV, back contact 35 of relay 2V, front contact 34 of relay IV, lower winding of relay P, front contact 33 of relay VP and front contact 32 of relay SAP, to Relay P opens its back contact 25, which de-energizes the control line for the next off period and which allows relays F and PP to drop.

A circuit is now closed for picking up relay 2V extending from front contact 31 of relay SA, back contact 38 of relay FP, front contact 39 of relay VP, front contact 46 of relay IV and winding of relay 2V, to Relay 2V closes a stick circuit for itself by way of its front contact 41 to through front contact .31 of relay SA.

Relay P is now released since the above described energizing circuit through its lower winding is interrupted at back contact 35 of relay 2V.

This results in closing back contact 25 for again energizing the line and picking up relays F and FP.

Relay VP is now released by means of a circuit from (B), front contact 48 of relay VP, front contact 43 of relay 2V, lower winding of relay VP The current in this circuit is effective to release relay VP, because it is of opposite polarity from the current flow through its upper winding. As soon as the contacts 45 and 38 of relay VP break, there is no circuit for energizing this relay and it remains down.

A circuit is now closed for picking up relay P extending from back contact 36 of relay LV, front contact 35 of relay 2V, upper winding of relay P, back contact 33 of relay VP and front contact 32 of relay SAP, to The operation of relay P opens the control line circuit which results in dropping relays F and PP. A circuit is now closed for picking up relay LV extending from front contact 31 of relay SA, back contact control line since this is the end of the cycle..

Relay S is dropped, by reason of its stick circuit being opened at front contact 20 when relay SA releases. With relay S down, front contact 24 is opened which further maintains the control line in ole-energized condition.

It is to be understood that these circuit connections may be continued for as many steps as desired, with the pick-up and stick circuits of the stepping relays and the steering or half step relay extended in an obvious manner. Relays IV 2V and VP of Fig. 3 operate in synchronism with corresponding relays of Fig. 2.

The pick-up circuits of the stepping relays shown in Fig. 3 extend from front contact I31 of relay SA back contact I38 of relay FP (operating in synchronism with relay FP in the control Ofi'lCS). The extension of this circuit to the stepping relay windings is through back and front contacts I39 of relay VP which circuit is identical with that of Fig. 2. Consequently it is not believed necessary to specifically describe the stepping relay operation at the field station.

From the above description, it will be observed that the stepping relays are picked up in rotation during successive off periods and the steering relays are shifted during succeeding on periods, that is, they pick up during the odd on periods and drop during the even on periods.

Polarity selection of impuZses.-As above pointed out, during a cycle of operations started manually from the control office, the first impulse in the control line is due to the fact that relay CS is normally positioned to the right. This impulse fixes the cycle as a control cycle by leaving relay CK down and. picking up relay CK Assuming that the stepping relays pick up as above described, the first control impulse to be applied to the control line after the conditioning impulse above described, is determined by the connection of code jumper 59. For example, with jumper 59 connected to (B), as shown in Fig. 2, a circuit is completed for actuating relay CS to its left hand dotted position which extends from (3-), jumper 55, front contact 5| of relay CD, front contact I2 of relay IV, back contact I3 of relay 2V and winding of relay CS, to (CN). This conditioning circuit of relay CS is effective during the off period, since relay IV is picked up at the time the control line is de-energized.

When the control line is next closed, it will be energized with potential from battery OB, by way of contact 28 of relay CS in its left hand dotted position, front contact 24 of relay S, winding of relay F and back contact 25 of relay P, to line conductor I0.

Should jumper 59 be connected in its alternate position which leads to (3+), then the conditioning circuit for relay CS would result in positioning this relay to the right, which would be effective to energize the control line with a potential from battery OB. Therefore, the selective connection of jumper 50 to- (3+) or (B) selectively conditions, during an off period, the polarity withrwhich the control line is to be energized during the succeeding on period.

During the second off period when rel'ay 2V is picked up, the circuit of relay CS is extended by way of front contact I3 of relay 2V and front contact 52 of relay CD, to switch machine lever SML. If the contacts of lever SML are in a right hand reverse position, (B) potential is applied to the code sending relay CS. This circuit extends through contact 53 of lever SML in its right hand dotted position. With lever SML in its left hand normal position, a circuit is extended from (B+), through contact 53 in its left hand position, over the above described circuit to relay CS, which results in actuating this relay to its right hand position.

It will thus be seen that the potential selected by front contacts I2 and I3 of relays IV and 2V respectively, causes the actuation of the polar contacts of relay CS to a proper position for determining the desired polarity of the next succeeding impulse to be applied to the control line, upon the closure of back contact 25 of impulsing relay P.

Upon the closure of back contact 25, line relays F and F are energized with a polarity dependent upon the position of contacts 23 and 28 of relay CS, but irrespective of the polarity of the impulse, the line repeating relays FF and FP are energized and their contacts immediately pick up.

From the above it will be observed that different code combinations, on a choice of two per step, may be chosen for selecting field stations by arranging the connection of jumper 50 in either one of two positions. It will be obvious that, while only two code combinations are obtained on one step, this arrangement can be extended so that'another code jumper provided for the second step, would likewise be capable of selecting one of two code combinations, which would result in a selection of four stations on two steps. It will also be understood that more than one step may be provided for selecting additional control devices, similar to lever SML and that the positions of such devices may be repeated during additional steps of the stepping relay bank.

Transmission of controZs.Assuming that relay IV at the field station shown in Fig. 3 is up, and that the control line is energized with a potential from battery OB as above explained, this potential causes relay F to actuate its contacts to the left hand dotted position. An execution circuit is closed during this period which governs pilot relay PT This circuit extends from (3-), contact I32 of relay F in its left hand dotted position, front contact I3I of relay SAP back contact I40 of relay L0 back contact I4I of relay 2V front contact I42 of relay IV to the lower winding of relay PT Since the same potential is applied to both terminals of this winding, relay PT remains down.

In the event that the first code selecting impulse applied to the line is then relay F would close a circuit from (B+), contact I32 in its right hand dotted position, over the remainder of the above described circuit to the lower winding of relay PT. In this event, opposite potentials from the battery are applied to the terminals of the lower winding of relay PT which results in this relay picking up. When it is picked up, it closes a stick circuit for itself during the remainder of the cycle which extends from front contact I33 of relay SA front contact I43 of relay PT 'and upper winding of this relay, to

When relay 2V is picked up, a circuit is completed for picking up station relay ST which extends from front contact I3'I of relay SA front contact I44 of relay 2V terminal I45, back contact I46 of relay L0 front contact I41 of relay PT and winding of relay ST to It will be apparent that terminal I may be'connected to higher numbered stepping relays in systems of larger size, so that the station relay may be picked up on some step other than the second as shown in this embodiment.

While a-selection of only two stations is shown in Figs. 2 and 3, it will be understood that a selection of four stations may be obtained by providing an additional jumper in the control office, as above mentioned and by providing an additional pilot relay (PT not shown) at the field station, which would or would not be picked up as determined by the polarity of the impulse applied to the line, after the second stepping relay is actuated. In this event, station relays similar to relay ST would be connected to the four selective circuits of relays PT and PT one station relay at each station. It is to be noted that in the disclosure of Fig. 3, a station relay similar to relay ST at the second station will be connected to back contact I4! of the pilot relay similar to relay PT at the second station.

An execution circuit is closed for controlling switch machine control relay SMR on the second step, which extends from contact I32 of relay F selectively connected to (B+) or (B), front contact I3I of relay SAP back contact I40 of relay L0 front contact I4I of relay 2V front contact I48 of relay ST and winding of relay SMR to (ON). Relay SMR actuates its polar contact I49 to a right or left hand position, depending upon whether or potential respectively is applied to the winding of this relay.

With contact I49 of relay SMR. in a right hand position, potential is applied to the normal operating winding of the switch machine 8M With polar contact I49 of relay SMR in a left hand dotted position, potential is applied to the reverse operating winding of the switch machine SM This energization of the normal and reverse windings of the switch machine results in corresponding operations of the machine, for moving the track switch T8 to normal or reverse locked positions in the well known manner.

In brief, the positioning of control lever SML determines the polarity applied to the switch machine control relay SMR which in turn governs the operation of the switch machine. Obviously, if the control lever is moved to a position out of correspondence with the position of the track switch, this switch will be operated, but if the control lever is in a position which corresponds with the position of the track switch, this switch will not be operated.

The transmission of controls continues until the predetermined number of steps have been 7 taken, which by way of example has been specifically illustrated as including two steps, one of which is employed for station selection and one 7 for transmission of controls to the selected station.

trol ofiice. The stick circuit of the stepping relays and the VP relay is now opened and all the relays at the field station, which have been operated during the control cycle are restored to normal.

Transmission of indications-The system may be initiated into a cycle of operations from its normal period by an automatic change at a field station. Such initiation may be due to a change in traflic conditions or to the operation of a traffic controlling device to a new position as a result of controls transmitted from the ofiice.

For example, track switch TS of Fig. 3 may be shifted from a normal to a reverse position in response to a control transmitted by lever SML, in a manner previously described. When the track switch responds to such a control it causes a relay (not shown) to momentarily interrupt the stick circuit of change relay CH Similarly, track relay T may be released by a change in traffic conditions, caused by a train passing over the associated detector track circuit, in accordance with the usual practice. The release of relay T likewise interrupts the stick circuit of relay CH In brief, the stick circuit for the change relay CH is carried through front and back contacts of the track relay T and may similarly be carried through like contacts of other traffic controlling devices associated with the field station. Irrespective of the particular change which occurs, the dropping of relay CH closes a pick-up circuit for start relay STR extending from back contact I55) of relay CH back contact I5I of relay SAP and winding of relay STR to Relay STR closes a circuit for picking up lookout relay L0 which extends from front contact I52 of relay STR back contact I35 of relay CK and lower winding of relay L0 to Relay LO opens, at its back contact I 2%, the control line conductor extending to other stations toward the end of the line and at front contact I26 it connects battery F13 to the line leading to the control office. Current from battery F13 extends from the terminal of this battery, back contact I53 of relay CS line conductor II, back contact 24 of relay S (Fig. 2) winding of relay F, back contact 25 of relay P, line conductor I9, winding of relay F front contact I26 of relay L0 and back contact I 54 of relay CS to the terminal of battery FB The current flow in this circuit is in the proper direction for positioning relays F and F to the left. Relay F closes a pick-up circuit for relay CK extending from (B), contact 26 of relay F in its left hand dotted position, back contact 27 of relay SAP and upper winding of relay CK, to (13+). Relay F connects (B) through its contact I32 in a left hand dotted position and back contact I3I of relay SAP to the lower winding of relay CK and since the same potential is applied to both terminals of this winding, relay 0K is not picked up.

Relay FP in the control ofilce and relay FP at the field station are now picked up over obvious circuits and relays SA, SAP, SA and SAP are likewise operated, by means of circuits which have been previously described.

Relay SA closes a stick circuit for relay CK, before the pick-up circuit of this relay is opened at back contact 21 of relay SAP. This stick circuit extends from front contact Id of relay SA, front contact I5 of relay CK and lower winding of relay OK, to Relay CK opens contacts I8 and 22 which are included in the pick-up and stick circuits of relay S, so that there is no possibility of this relay being up during an indication cycle.

When relay SA at the station is picked up, a stick circuit for relay L0 is established extending from front contact I33 of relay SA back contact I34 of relay 0K front contact I55 of relay L0 and upper winding of relay L0 to Relay LO opens its back contact I4!) included in the control executing circuit, so that the control circuit governed by contact I32 of relay F is ineffective. Relay SAP opens, at its back contact IEI, the pick-up circuit of relay STR and this relay is dropped.

. With relays SA, SAP and SA picked up, proper circuits are closed so that the stepping relays in the control ofiice' and at the field station are operated by impulses in the line, as repeated by relays FF and FP Likewise, the line circuit is impulsed by means of relay P in the manner previously described. During an indication cycle, relay CS in the control office is ineffective to connect battery 013 to the control line conductor, since the front contact 24 of relay S is open. After the first stepping relay in the control office is picked up, relay CS is not again energized because relay CD is down.

Since relay CK at the field station is down, relay CS is energized or deenergized in accordance with the energized or deenergized condition of the circuit extending through back contact I36 of relay 0K For example, if code jumper 558 is connected to as shown in Fig. 3, then when the first stepping relay IV is picked up, a circuit is closed for picking up relay CS which extends from jumper I56, front contact I51 of relay iV back contact I58 of relay 2V back contact E35 of relay 0K and winding of relay CS to This circuit picks up relay CS during the off period when relay IV picks up and preconditions the polarity to be applied to line It during the next on period. With relay CS up, the side of battery FB is connected through front contact I53 of relay CS line II, back contact 2 of relay S, winding of relay F, back contact 25 of relay P, line It, winding of relay F front contact I26 of relay L0 and front contact I54 of relay CS to the terminal of battery FB This current flows in such a direction that relays F and F will be positioned to the right. This distinctive positioning of relay F at the field station is ineffective, but positioning relay F in the control office to the right closes a circuit which extends from (B+), contact25 of relay F in its right hand position, front contact 2'5 of relay SAP, back contact I9 of relay S, back contact as of relay LV, back contact 55 of relay 2V, front contact 56 of relay IV to the upper winding of relay iPT. Current in this circuit is effective to pick up relay I PT, after which it is stuck up over a circuit extending from front contact IA of relay SA, front contact 57 of relay IPT and the lower winding of relay IPT, to

In the event that code jumper I56 is connected in its alternate dotted line position, then with relays I V and IV picked up and the line circuit energized, relays F and F are actuated to their left hand positions, because relay CS remains down, connecting battery FB to the line circuit in such a direction that the terminal of this battery is applied to the control line conductor and returns by way of the return conductor, to the terminal.

With relay F positioned to the left, the above described circuit, leading to the upper winding of relay I PT is not effective to pick up this relay, because contact 26 of relay F in its left hand dotted position connects to (B) and the opposite terminal of relay iPT is connected to the same terminal of the battery.

It will be understood that additional pilot relays, similar to relay IPT may be provided and positioned during additional steps, in which event additional steps at the field station would connect to additional jumpers similar to I56. It is obvious that the provision of one pilot relay results in the registration of two stations, one station being registered by relay ST, which is connected to front contact 58 of relay IPT and another station being registered by an additional station relay, similar to relay ST connected to back contact 58 of relay IPT.

It will also be apparent that the provision of one additional pilot relay will result in accommodating four station relays, by pyramiding the contacts of the pilot relays in the well known manner. Briefly, a pilot relay in the control office and a code jumper at the field station for each step, provides means for registering a number of stations in the control office, which number equals two raised to the power of the number of steps.

The circuit for picking up relay ST of Fig. 2, when relay IPT is picked up, extends from front contact 31 of relay SA, front contact 41 of relay 2V, terminal 59, front contact 60 of relay CK, front contact 58 of relay IPT and winding of relay ST, to Terminal 59 is shown connected to the terminal of relay 2V, so that the selected station relay is picked upon the second step. This terminal 59 may be connected to the winding of some other stepping relay, so that the selected station relay may be picked up on any step desired.

When the line circuit is energized after the station has been registered in the control oflice, the indication storing relay IR is energized in accordance with the position of polar contact 26 of relay F. This occurs after the system of the present embodiment has taken the second step. Assuming that the track relay T is energized, relay CS will be deenergized and current from battery FB will flow in line conductor II] in series with line relays F and F returning by way of conductor II to the terminal of battery FB This positions relay F to the left, which is effective to apply (B-), through contact 26 of relay F in its left hand dotted position, front contact 21 of relay SAP, back contact I9 of relay S, back contact 54 of relay LV, front contact 55 of relay 2V, front contact 49 of relay ST and winding of relay IR, to (CN). Polar contact 6| of relay IR is positioned to the right which leaves lamp OS dark as an indication that the detector track section TS is unoccupied.

Should the detector track section be occupied. relay T would be deenergized and a circuit would be closed from through its back contact I59,

front contact I58 of relay 2V back contact I36 7 of relay 0K and winding of relay CS to This would pick up relay CS and at its front contacts I55 and I54, battery FB would be connected to the line conductors in such a direction that relay F would be positioned to the right.

The circuit through polar contact 26 of relay F would then be from (B+), by way of its right hand dotted position to relay IR. This would actuate relay IR to its left hand dotted position for closing a circuit throughits contact 6 I, which would light lamp OS as an indication that de-' tector track switch TS is occupied.

It is to be understood that, although an indicator lamp OS has been illustrated for advising the operator of a condition at the field station, other suitable indicator means such as audible warnings, miniature movable track switch points or the like may be employed when desired. It is also to be understood that additional indication storing relays, similar to relay IR may be provided and conditioned on additional steps for displaying additional indications similar to OS when necessary.

Plurality of stored start conditions.In the event of several stored ofiice and field start conditions, the communication system functions to send controls until all stored controls have been taken care of. After this, the communication system is used for the transmission of indications on separate cycles. Assuming that there are severa1 stored o-fiice and field start conditions, there will be several storing relays similar to relay SR picked up, so that relay S will be picked up at the end of each cycle. Relay S will be stuck up after the cycle is finally started as previously explained and relay CK cannot be picked up because the first impulse will be for closing contact 25 of relay F in its right hand dotted position. This condition is repeated dur ing each cycle until all of the stored controls have been transmitted.

When there is a field station with stored indications to send and the control oilice has a simultaneous stored control condition at the time the system reaches the end of an operating cycle, the following series of operations take place: the control ofiice relay S picks up, which connects battery OB to the line circuit. At the field station, relay L0 is picked up over the circuit through front contact I52 of relay STR Since relay CS is in its right hand position and relay CS is down at this time, the terminals of both batteries OB and FB are connected to line ID, with the result that this line is not energized. Relay L0 closes a circuit for picking up relay SAP extending from back contact I29 of relay FP front contact I60 of relay L0 and winding of relay SAP to Relay SAP opens the pick-up circuit of relay S'IR and due to the slow acting characteristics of relay STR it drops after a short interval of time, causing the release of relay LO by opening front contact I52. The line is now energized from battery OB, including back contact I26 of relay L0 conductor I64, connection I2! and the return line conductor I I, which circuit is disconnected from one terminal of battery FB The control ofllce now sends its controls and relays F FP SA and SAP pick up in turn. Since the circuit of relay STR is open at back contact I5I of relay SAP relay STR must wait until the end of this cycle before it can again be picked up.

Should there be a plurality of field stations with indications to transmit under the above conditions, the same series of events take place, first at the station nearest the control office and thereafter at other stations along the line until the line circuit is reestablished as indicated in Fig. 3, when the transmission of controls begins.

As soon as the control office sends the conditioning impulse over the control line, relays similar to relay F are actuated to their right hand dotted positions, which is effective to pick 75 up, the. checking relays, similar to relay 0K at the various stations. This results in, opening the pick-up circuitsof-all the look-out relays at back contacts2 similar to I35, as well; as the stick circuits of all lock-out relays at back contacts similar to I34. Therefore, all the look-out relays will be down and the, system will; function for the transmission of controls.

Lockeout between field stations.1n the. event that changes have taken place, at several field stations simultaneously or in rapid succession, so, that more than one field station has indications to transmit at the beginning of a cycle. (and no controls are ready to transmit) it. is necessary to provide means for preventing more than one station from obtaining access to the communication circuit at one time. In this embodiment preference is given to the field station nearest the control ofiice.

It is believed that the look-out feature may be best understood by assuming that two relays similar to relay STIR. are picked up at the same time due to two relays similar to. relay CH being down at the same time. It will be explained how only the station nearest the control oflice effects control of the communication system under this condition. It will beunderstood that the operation is the same when more than two relays similar to relay STR are up at the same time, since only the station nearest the control ofilce will be able to transmit indications. At the start of the next cycle the station next in order nearest the office will obtain access to the communication system.

It will be understood thatwhen two relays similar to relay S'IR are up at the same time, the above described circuit for picking up relay LO. is effective to pick up the two lock-out relays at the stations having indications to transmit.

When the conditioning impulse is applied to the line circuit, relays F FP SA and SAP at the station nearest the control office are picked up. Relays similar to F FE and SA at the station farthest from the control oiiice are not picked up, because control line conductor I 64 leading to this station is open at back contact I26 of relay LO at the station nearest the office. Therefore, the station nearest the office is the only one which can have its line relay F impulsed, because the others are open. The relay similar to relay LO at the farther station closes a circuit for picking up the relay similar to relay SAP which extends from back contact I29 of the relay similar to F1 front contact I50 of the relay similar to relay L0 and Winding of the relay similar to relay SAP to This is effective to open the circuit of the starting relay, similar torelay STR at back contact IEI so that this relay releases and interrupts the pick-up circuit of the look-out relay at contact I52. The lock-out relay is dropped because its stick circuit is open at contact I33 at this farther station. When the relay similar to relay L0 releases, the circuit of the relay similar to relay SAP is interrupted and this relay is released, which places the circuits at the fartherstation in normal condition, from which they may be again initiated. This station will get its chance to seize the communication line at the start of the next cycle.

At the station nearer the control ofiice line relay F is energized which effects the pickingup of relays FP SA and SAP in sequence. The closure of front contact I33 of relay SA providesa, stick circuit for relay L0 at this station, The transmission from this Station is then effected as previously described,

It will now be explained, how change relay CH at the field station is reset, after it has been dropped to initiate a cycle of indications. With lock-out relay L0 picked up, a circuit is closed, after the first step-ping relay is picked up, extending from front contact Itl, ofrelay L0 back contact I62 of relay 2V front contact I63 of relay IV and upper winding of relay CH to This picks up the change relay at the, time the first step is taken and when the second step is, taken the above described circuit is opened at back contact I62 of relay 2V Relay CH has its stick circuit now established so that it is in condition to be subsequently released when the station has other indications to transmit.

Having thus described one specific embodiment of a centralized traflic controlling system, it is desired to be understood that the particular arrangements illustrated are only typical illustrations of applicants invention and are not intended to illustrate the exact circuit design necessary to carry out the features of the invention, but this form has been selected to facilitate in the disclosure rather than to limit the number of forms which it may assume and it is further desired to be understood that various modifioations'may be made in order to meet the various problems encountered in practice and the system may be varied in the number of field stations to which the invention is applied and the amount of apparatus installed at a particular field station, all without in any manner departing from the spirit or scope of the present invention except as limited by the appended claims.

What I claim is:

1. In a centralized traffic controlling system of the selector type, the combination with a control office and a plurality of field stations, of a single. line circuit connecting said control ofiice with said field stations, impulsing means at said control ofiice for opening and closing said line circuit to condition a plurality of impulses to comprise a cycle of operation, a source of current at said control office and at each of said field stations, code selecting means at said control ofiice and at each of said field stations for applying impulses from its respective source and for determining the character of such impulses, and means for preventing more than one code selecting means from being effective during any one cycle of operation, whereby messages are transmitted out from said control office and back from any one of said field stations during separate cycles of operation.

2. In combination, first and second control 10- cations, a line circuit connecting said control. locations, means'including a source of current at said first location for energizing said line circuit to cause current to flow in one direction, means including a source of current at said second location for energizing said line circuit to cause current to fiow in the opposite direction, whereby there is an absence of current flow upon the simultaneous connection of both said sources, means at said second location responsive to the absence of current flow in said line circuit when its said source is connected to said line circuit for automatically disconnecting its said source, whereby said source at said first location is effective to cause current to flowin said one direction, and means responsive to current flow in said one direction and said opposite direction for transmitting messages from said first to said second location and from said second to said first location respectively.

- 3. In combination, first and second control 10- cations, 'a single normally closed deenergized line circuit connecting said control locations, means including a source of current at said first location for energizing said line circuit to cause current to flow in one direction, means including a source of current at said second location for energizing said line circuit to cause current to fiow in the opposite direction, whereby there is an absence of current fiow upon the simultaneous connection of both said sources, means at said second location responsive to the absence of current flow in said line circuit when its said source is connected to said line circuit for only after a predetermined time automatically disconnecting its said source, whereby said source at said first location is effective to cause current to flow in said one direction, and means responsive to current flow in said one direction and said opposite direction for transmitting messages from said first to said second location and from said second to said first location respectively.

4. In combination, a control oifice, a field station, a line circuit connecting said control office and said field station, code transmitting means at said control ofiice for impressing a plurality of different series of positive and/ or negative impulses on said line circuit with the first impulse of each series being of a particular polarity, code transmitting means at said field station for immeans at said field station responsive to the ab-' sence of current flow when both said code transmitting means impress the first impulse of a series simultaneously to said line circuit for automatically causing its said code transmitting means to Withdraw and allow operation of said code transmitting means at said control ofiice.

5. In a centralized traific controlling system, a control ofiice, a plurality of field stations, a two-wire line circuit connecting said control office with said field stations, impulse timing means in said control office, means at said control oifice governed by said impulse timing means for intermittently and distinctively energizing said line circuit from a source of current in said control oflice for providing a series of distinctive impulses, means at each field station governed by said impulse timing means for intermittently and distinctively energizing said line circuit from a source of current at such field station for providing a series of distinctive impulses, and means at said control office and at each of said field stations responsive to the first impulse of any series except its own for preventing said code transmitting means at that station from transmitting.

6. In a centralized trafiic controlling system; a control office; a plurality of field stations; a normally deenergized closed line circuit connecting said control office with said field stations; a source of direct current at said control ofiice and at each of said field stations; code transmitting means at said control office and at each of said field stations for applying different series of distinctive impulses to said line circuit from said source of direct current at such station; lockout means at each station effective, only while there is the absence of a series of impulses on said line circuit and prior to the application of the first impulse of a series by its said code transmitting means, to interrupt said line circuit extending to all field stations farther from said control ofllce and to apply potential in accordance with the character of the first impulse of a series of impulses to said line circuit extending to said control ofiice, means at said control ofiice and at each field station for determining that the character of the first impulse of every series shall be such that there shall be an absence of current flow in said line circuit provided said control office code transmitting means and said code transmitting means at any particular station operates to apply the first impulse of a series of impulses simultaneously, means at each field station responsive to the absence of current flow in said line circuit, when its said lockout means is efiective, to remove potential from said line circuit as applied from its said direct current source, whereby said control ofiice is effective to cause current flow; means at said control-office responsive to said different series of impulses transmitted by said field station; and means at each field station responsive to said different series of impulses transmitted by said control oifice.

7. In a centralized traffic controlling system, a control ofiice, a plurality of field stations, a line circuit connecting said control ofi'ice with said field stations, a source of direct current at each of said field stations, a code transmitter including the source of current at each of said field stations, means including said code transmitter and its source for energizing said line circuit with different series of distinctive impulses, lock out means at each station effective prior to the energization of said line circuit by an impulse of a series to interrupt said line circuit to all succeeding field stations, means at each station responsive to those stations preceding a transmittmg station to the first impulse of a series to prevent said code transmitter at such station from becoming effective until the end of that series of impulses then being impressed on said line circuit, and means at said control office distinctly responsive to each different series of impulses impressed on said line circuit.

8. In a remote control system, a control oflice, a plurality of field stations, a two-wire line circult connecting said control oflice with said stations, means at said control office for intermittently and reversibly energizing said line circuit from a first source of current in said control ofiice :for providing a first series of polar impulses, means at each field station for intermittently and reversibly energizing said line circuit from a second source of current at the associated field station for providing a second series of polar impulses, means at said control ofiice for marking the first impulse of said first series With one polarity, means at each field station for marking the first impulse of said second series with another polarity, and means governed by the first impulse of a series being of said one polarity or said another polarity for determining that said first or said second source of current respectively shall be used for the succeeding impulses of the series.

THOMAS J. JUDGE. 

